When you're passed the point of something being hilariously funny; when you've laughed as hard as you possibly can. Often expressed online by putting an asterisk (*) in front of and behind the word itself.

Ashley: So I went out with this guy last night, and we hit it off, but he doesn't seem to be interested in me other than my clothes and who does my hair.
Mary: That boy has more zest than a bag full of lemons.
Ashley: *DEAD*

MOM: ".. oh my god, son.. the president is DEAD... he was shot by a farmer riding a camel.."
SON: ".. oh no.. What'd they do to the farmer?"
MOM: "They gave him a time-out for ten minutes and told him not to do it again"
SON: "Wow they're getting harsher on punishment these days, we should protest .. and make up some false allegations of police brutality!"
MOM: "GOOD IDEA"